American aircraft bombed positions held by Islamic State insurgents in northern Iraq on Friday in the first major US military action there since it withdrew troops in 2011, the Pentagon said.
Photo: Two F/A-18 aircraft dropped laser-guided bombs on a mobile artillery piece near Erbil. (AFP/US Navy/Joshua Card)
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The strikes came after militants shelled positions near the Kurdish region's capital of Erbil, hours after president Barack Obama publicly authorised the use of force to avert a "genocide".
Two US F/A-18 aircraft dropped 225-kilogram, laser-guided bombs on a mobile artillery piece of Islamic State (IS), the Sunni extremist movement that has swept across Iraq and Syria, Pentagon spokesman Rear Admiral John Kirby said.
Rear Admiral Kirby said that the strike, carried out at 1:45pm local time (8:45pm AEST), was ordered after the IS shelling was deemed a risk to US personnel based in Erbil, long considered a safe city in the troubled country.
"The decision to strike was made by the US Central Command commander under authorisation granted [to] him by the commander in chief," he said.
"As the president made clear, the United States military will continue to take direct action against [Islamic State militants] when they threaten our personnel and facilities."
The Pentagon later confirmed a second wave of air strikes near Erbil, destroying a militant convoy and killing a mortar team.
In Iraq, army chief of staff Lieutenant General Babaker Zebari hailed the strikes, telling the AFP news service that the raid will mean "huge changes on the ground".
Mr Obama pledged a limited mission to defend Erbil and break the IS siege on a group of thousands of members of the Yazidi minority fleeing the combat and sheltering on a mountain side.
On Thursday, the United States dropped thousands of litres of drinking water and 8,000 packaged meals to Yazidis who risk starvation as they cram onto Mount Sinjar.
"We can act, carefully and responsibly, to prevent a potential act of genocide," Mr Obama said in a televised address.
"We plan to stand vigilant and take action if they threaten our facilities anywhere in Iraq, including the consulate in Erbil and embassy in Baghdad," he said.
But Mr Obama, who rose to political prominence as an outspoken critic of his predecessor George W Bush's 2003 invasion of Iraq, said he would not send US ground forces back into the country.
"As commander in chief, I will not allow the United States to be dragged into fighting another war in Iraq," Mr Obama said.
"And so even as we support Iraqis as they take the fight to these terrorists, American combat troops will not be returning to fight in Iraq, because there is no American military solution to the larger crisis in Iraq."
US officials have made clear they do not anticipate a long-term campaign to eliminate IS as they press Iraq's Shiite-dominated government to reach out to the Sunni minority.
White House spokesman Josh Earnest said on Friday that Mr Obama had not established a "specific end date" for the military strikes in Iraq.
"We're going to sort of take this approach in which those kind of decisions are evaluated regularly and are driven by the security situation on the ground as it relates to the safety and security of American personnel, but also as it relates to supporting the ongoing efforts of both Kurdish security forces and Iraqi security forces," he told reporters.
Mr Earnest said the US action could eventually include more military support to Iraqi security forces working to repel IS fighters once the country forms a new "inclusive" government.
After the strikes were launched, the Federal Aviation Administration banned all US civilian flights from flying over Iraq owing to "the potentially hazardous situation created by the armed conflict".
Minorities fear death at hands of militants
Earlier this week, Islamic State militants captured Iraq's biggest Christian town, Qaraqosh, prompting many residents to flee, fearing they would be subjected to the same demands the Sunni militants made in other captured areas: leave, convert to Islam or face death.
The Islamic State, considered more extreme than Al Qaeda, sees Iraq's majority Shiites and minorities such as Christians and Yazidis, a Kurdish ethno-religious community, as infidels.
Video: Peter Lloyd explains the march of IS across Iraq (ABC News)
UN secretary-general Ban Ki-moon said he was "deeply appalled" by reports of attacks by Islamic State militants in Iraq and called on the international community to help the country's government.
The UN Security Council was due to hold an emergency meeting on the crisis.
The Islamic State said in a statement on its Twitter account that its fighters had seized 15 towns, the strategic Mosul dam on the Tigris River and a military base, in an offensive that began on the weekend.
Kurdish officials say their forces still control the dam, Iraq's biggest.
On Thursday, two witnesses said Islamic State fighters had hoisted the group's black flag over the dam, which could allow the militants to flood major cities or cut off significant water supplies and electricity.
Thousands stranded on Sinjar mountain
The militants' weekend capture of Sinjar, ancestral home of the Yazidi minority, prompted tens of thousands of people to flee to surrounding mountains, where they are at risk of starvation.
Yazidis, regarded by the Islamic State as "devil worshippers", risk being executed by the Sunni militants seeking to establish an Islamic Caliphate and redraw the map of the Middle East.
Who are the Yazidis?
Who are the followers of a mysterious ancient faith surrounded by Islamic militants who now threaten to kill them all?Some of the many thousands trapped on Sinjar mountain have been rescued, a spokesman for the UN Office for the Coordination of Humanitarian Affairs said, adding that 200,000 had fled the fighting.
"This is a tragedy of immense proportions, impacting the lives of hundreds of thousands of people," spokesman David Swanson said by telephone.
Many of the displaced people urgently need water, food, shelter and medicine, he said.
A spokesman for the UN agency for children said many of the children on the mountain were suffering from dehydration and at least 40 had died.
Thousands of Iraqis, most of them Yazidis, are streaming to the border with neighbouring Turkey to flee the fighting, Turkish officials said.
Gains by the Islamic State have raised concerns that militants across the Arab world will follow their cue.
During the weekend, the Sunni militants seized a border town in Lebanon, though they appear to have mostly withdrawn.
The Islamic State poses the biggest threat to Iraq's integrity since the fall of Saddam Hussein in 2003.
The group has deepened sectarian tensions, pushing the country back to the dark days of the civil war that peaked in 2006-2007 under US-led occupation.
